Airflow Patterns And Flow Path of Airborne Particulates

This FREE Master Class is brought to you by TIPS: The Infection Prevention Strategy

FULL VIDEO PRESENTATION BELOW

Hospital-acquired infections has been persistent in hospitals and airborne transmission plays a role in many nosocomial infections. Air is the primary carrier of heat, moisture, contaminants, and airborne contaminants in health care facilities such as patient rooms, isolation rooms, and operating rooms. Therefore the flow path of supply air plays an important role in determining the flow path of airborne pathogens in these spaces. The airflow distribution also determines the thermal comfort of occupants, indoor air quality, distribution of surface contamination, and potential for transmission of airborne pathogens in a room. The airflow patterns, temperature distribution, and concentration of contaminants including the flow path of airborne pathogens in a patient room can depend on several inter-related factors including the location and type of supply diffusers, supply air flow rates (air change rates) and associated diffuser throws, supply air temperature, size and locations of room return, bathroom exhaust flow rates, locations and strengths of various heat sources in a room, arrangement of furniture and other obstructions to airflow, and importantly relative location of a patient in the room. In addition, orientation of the room can determine the solar sensible heat loads in the room. Several studies indicate that the design of a ventilation system and the resulting airflow patterns play a more important role in controlling the flow path of contaminants than just the supply airflow rate or air changes per hour (ACH) alone. This case study evaluates the impact of supply and return locations on the airflow patterns and temperature distribution along with the resulting thermal comfort of occupants, and probable flow path of airborne pathogens in a typical patient room using Computational Fluid Dynamics (CFD) simulations. These analyses indicate the linear diffusers combined with high supply air flow rates (high air change rates) can cause strong recirculation and entrainment (induction) flows in the room. Depending on the location of the return grille, the airborne particles released from the patient’s face can get entrained back into the supply air stream and can eventually spread into the entire room. However, this study indicates placement of a return grille right behind the linear supply diffuser over the patient’s head can potentially provide a ready flow path to airborne particles to exit out of the room without significant recirculation and entrainment back into the supply air stream. This study demonstrates that the supply air flow paths, induced air flow paths, and exhaust grille placement can work collaboratively to establish protective and effective contaminant control. The presentation with the help of insightful airflow animations will show the movement of airborne particles in a patient room and will demonstrate the important of locations supply and exhaust grills. This presentation will provide valuable insights to healthcare facilities managers, owners and design engineers in designing the HVAC systems for patient rooms.

Learning Objectives

  1. Review airflow patterns in a hospital patient room
  2. Evaluate the impact of airflow patterns on the thermal comfort and probable flow path of airborne pathogens in a patient room
  3. Evaluate the impact of locations of supply and return in a patient room on the probable flow path of airborne pathogens
  4. Understand of Computational Fluid Dynamics (CFD) be employed in the design and optimization of a resilient patient room

Full video of our June 11, 2020 Webinar:

SPEAKERS

Kishor Khankari, Ph.D.

Dr. Khankari provides engineering solutions and insights through Physics based simulation and CFD analysis. Kishor has several years of experience in providing CFD consulting services which lead to optimized solutions to a wide variety of engineering problems involving fluid flow, heat transfer, mass transfer, and other similar engineering processes. He provided consulting services to reputed firms including Yahoo!, Facebook, Dell, Ford, GM, York International, GE, Pratt & Whitney, Cummins, Delphi, Cargill, Ralston Purina, Warner Lambert, Lockheed Martin.

Dr. Khankari has developed a patented technology of a wind band design of exhaust fan assembly systems. He has developed several easy-to-use analytical software tools, which are regularly used by design engineers in a variety companies including those in the critical facility and automotive industries.
A noted expert in CFD, he has been regularly publishing in several technical journals and trade magazines. Dr. Kishor Khankari is ASHRAE Distinguished Lecturer and recipient of the ASHRAE Distinguished and Exceptional Service Awards.

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